U.S. patent application number 15/431994 was filed with the patent office on 2018-08-16 for turbine blades having shank features and methods of fabricating the same.
The applicant listed for this patent is General Electric Company. Invention is credited to Melbourne James Myers, Richard Ryan Pilson, Felipe Roman-Morales, Kevin Lee Worley, William Scott Zemitis.
Application Number | 20180230829 15/431994 |
Document ID | / |
Family ID | 63104480 |
Filed Date | 2018-08-16 |
United States Patent
Application |
20180230829 |
Kind Code |
A1 |
Zemitis; William Scott ; et
al. |
August 16, 2018 |
TURBINE BLADES HAVING SHANK FEATURES AND METHODS OF FABRICATING THE
SAME
Abstract
A method of modifying a shank of a turbine blade from an initial
profile to an undercut profile includes removing a first portion of
material from an underside of a downstream angel wing of the
turbine blade. The downstream angel wing extends axially from a
downstream cover plate of the shank. The method also includes
removing a second portion of material from a generally
axially-extending portion of the downstream cover plate adjacent a
dovetail of the turbine blade.
Inventors: |
Zemitis; William Scott;
(Simpsonville, SC) ; Pilson; Richard Ryan; (Greer,
SC) ; Roman-Morales; Felipe; (Simpsonville, SC)
; Myers; Melbourne James; (Woodruff, SC) ; Worley;
Kevin Lee; (Taylors, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Family ID: |
63104480 |
Appl. No.: |
15/431994 |
Filed: |
February 14, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02T 50/60 20130101;
F01D 5/3015 20130101; F05D 2230/10 20130101; F01D 5/081 20130101;
F05D 2250/74 20130101; F01D 5/147 20130101 |
International
Class: |
F01D 5/30 20060101
F01D005/30; F01D 5/14 20060101 F01D005/14 |
Claims
1. A method of modifying a shank of a turbine blade from an initial
profile to an undercut profile, said method comprising: removing a
first portion of material from an underside of a downstream angel
wing of the turbine blade, wherein the downstream angel wing
extends axially from a downstream cover plate of the shank; and
removing a second portion of material from a generally
axially-extending portion of the downstream cover plate adjacent a
dovetail of the turbine blade.
2. The method according to claim 1, wherein removing a first
portion of material comprises removing material having a maximum
thickness in a range of between about 0.070 inches to about 0.150
inches from the underside of the downstream angel wing.
3. The method according to claim 1, wherein removing a second
portion of material comprises removing material having a maximum
thickness in a range of about 0.020 inches to about 0.040 inches
from the generally axially-extending portion of the downstream
cover plate adjacent the dovetail of the turbine blade.
4. The method according to claim 1, further comprising removing a
third portion of material from a generally radially-extending
portion of the downstream cover plate radially inward of the
downstream angel wing.
5. The method according to claim 4, wherein removing a third
portion of material comprises removing material having a maximum
thickness in a range of about 0.050 inches to about 0.070 inches
from the generally radially-extending portion of the downstream
cover plate radially inward of the downstream angel wing.
6. The method according to claim 1, wherein removing a first
portion of material further comprises removing material to form the
undercut profile defined by a plurality of points having
coordinates listed in Table 1 subject to a tolerance of about
.+-.0.030 inches, the plurality of points joined with smooth
continuous arcs, wherein each of the coordinates for the T datum in
Table 1 is adjusted based on a difference between a datum distance
W2 of the turbine blade and a reference datum distance W2
associated with Table 1.
7. The method according to claim 1, further comprising defining a
shape of the underside of the downstream angel wing and a portion
of the downstream cover plate radially inward of the downstream
angel wing by a cylindrical rotation of the undercut profile
between a pressure side face of the shank and an opposite suction
side face of the shank.
8. The method according to claim 1, further comprising defining a
shape of the underside of the downstream angel wing and a portion
of the downstream cover plate radially inward of the downstream
angel wing by a straight translation of the undercut profile
between a pressure side face of the shank and an opposite suction
side face of the shank.
9. A method of modifying a shank of a turbine blade from an initial
profile to an undercut profile, said method comprising: removing a
first portion of material from an underside of a downstream angel
wing of the turbine blade, wherein the downstream angel wing
extends axially from a downstream cover plate of the shank; and
removing a third portion of material from a generally
radially-extending portion of the downstream cover plate radially
inward of the downstream angel wing.
10. The method according to claim 9, wherein removing a first
portion of material comprises removing material having a maximum
thickness in a range of about 0.070 inches to about 0.150 inches
from the underside of the downstream angel wing.
11. The method according to claim 9, wherein removing a third
portion of material comprises removing material having a maximum
thickness in a range of about 0.050 inches to about 0.070 inches
from the generally radially-extending portion of the downstream
cover plate radially inward of the downstream angel wing.
12. The method according to claim 9, further comprising removing a
second portion of material from a generally axially-extending
portion of the downstream cover plate adjacent a dovetail of the
turbine blade.
13. The method according to claim 12, wherein removing a second
portion of material comprises removing material having a maximum
thickness in a range of about 0.020 inches to about 0.040 inches
from the generally axially-extending portion of the downstream
cover plate adjacent the dovetail of the turbine blade.
14. The method according to claim 9, wherein removing a first
portion of material further comprises removing material to form the
undercut profile defined by a plurality of points having
coordinates listed in Table 1 subject to a tolerance of about
.+-.0.030 inches, the plurality of points joined with smooth
continuous arcs, wherein each of the values for the T datum in
Table 1 is adjusted based on a difference between a datum distance
W2 of the turbine blade and a reference datum distance W2
associated with Table 1.
15. The method according to claim 9, further comprising defining a
shape of the underside of the downstream angel wing and a portion
of the downstream cover plate radially inward of the downstream
angel wing by a cylindrical rotation of the undercut profile
between a pressure side face of the shank and an opposite suction
side face of the shank.
16. The method according to claim 9, further comprising defining a
shape of the underside of the downstream angel wing and a portion
of the downstream cover plate radially inward of the downstream
angel wing by a straight translation of the undercut profile
between a pressure side face of the shank and an opposite suction
side face of the shank.
17. A turbine blade comprising: an airfoil that extends radially
between a root end and a tip end; a platform coupled to said root
end; a shank that extends radially inwardly from said platform,
said shank comprising a downstream cover plate and a downstream
angel wing that extends axially from said downstream cover plate;
and a dovetail that extends radially inwardly from said shank,
wherein a profile of an underside of said downstream angel wing and
a portion of said downstream cover plate radially inward of said
downstream angel wing is defined by a plurality of points having
coordinates listed in Table 1 subject to a tolerance of about
.+-.0.030 inches, said plurality of points joined with smooth
continuous arcs, wherein each of the coordinates for the T datum in
Table 1 is adjusted based on a difference between a datum distance
W2 of said turbine blade and a reference datum distance W2
associated with Table 1.
18. The turbine blade according to claim 17, wherein said shank
further comprises a pressure side face and an opposite suction side
face, said downstream cover plate extending therebetween, and
wherein a shape of said underside of said downstream angel wing and
said portion of said downstream cover plate radially inward of said
downstream angel wing is defined by a cylindrical rotation of said
profile between said pressure side face and said suction side
face.
19. The turbine blade according to claim 17, wherein said shank
further comprises a pressure side face and an opposite suction side
face, said downstream cover plate extending therebetween, and
wherein a shape of said underside of said downstream angel wing and
said portion of said downstream cover plate radially inward of said
downstream angel wing is defined by a straight translation of said
profile between said pressure side face and said suction side
face.
20. The turbine blade according to claim 17, wherein said turbine
blade has a datum distance W2 substantially equal to the reference
datum distance W2 associated with Table 1.
Description
BACKGROUND
[0001] The field of the disclosure relates generally to rotary
machines, and more particularly, to a blade that includes shank
features that facilitate reducing stress peaks and gradients within
the shank.
[0002] At least some known rotary machines include a compressor, a
combustor coupled downstream from the compressor, a turbine coupled
downstream from the combustor, and a rotor shaft rotatably coupled
between the compressor and the turbine. Some known turbines include
at least one rotor disk coupled to the rotor shaft, and a plurality
of circumferentially-spaced turbine blades that extend outward from
each rotor disk to define a stage of the turbine. Each turbine
blade includes an airfoil that extends radially outward from a
platform towards a turbine casing.
[0003] At least some known turbine blades include a shank and
dovetail radially inward of the platform to facilitate coupling the
blade to the rotor disk. An operational life cycle of at least some
turbine blades is limited at least in part by fatigue induced as a
result of a mean stress field and a vibratory stress field
converging to form a stress concentration in an interface defined
between the blade dovetail and the blade shank.
[0004] To facilitate reducing stress concentrations, at least some
known turbine blades include dovetail backcuts designed to relieve
stresses in the shank-to-dovetail interface. However, because of
increased complexity and an associated expense of manufacture of
the turbine blade, based on a location and amount of material that
must be removed, an effectiveness of using dovetail backcuts may be
limited. Additionally or alternatively, at least some known
dovetail backcuts require complementary modifications to the rotor
disk as well, which also increases the cost of manufacturing.
BRIEF DESCRIPTION
[0005] In one aspect, a method of modifying a shank of a turbine
blade from an initial profile to an undercut profile is provided.
The method includes removing a first portion of material from an
underside of a downstream angel wing of the turbine blade. The
downstream angel wing extends axially from a downstream cover plate
of the shank. The method also includes removing a second portion of
material from a generally axially-extending portion of the
downstream cover plate adjacent a dovetail of the turbine
blade.
[0006] In another aspect, a method of modifying a shank of a
turbine blade from an initial profile to an undercut profile is
provided. The method includes removing a first portion of material
from an underside of a downstream angel wing of the turbine blade.
The downstream angel wing extends axially from a downstream cover
plate of the shank. The method also includes removing a third
portion of material from a generally radially-extending portion of
the downstream cover plate radially inward of the downstream angel
wing.
[0007] In another aspect, a turbine blade is provided. The turbine
blade includes an airfoil that extends radially between a root end
and a tip end, and a platform coupled to the root end. The turbine
blade also includes a shank that extends radially inwardly from the
platform. The shank includes a downstream cover plate and a
downstream angel wing that extends axially from the downstream
cover plate. The turbine blade further includes a dovetail that
extends radially inwardly from the shank. A profile of an underside
of the downstream angel wing and a portion of the downstream cover
plate radially inward of the downstream angel wing is defined by a
plurality of points having coordinates listed in Table 1 subject to
a tolerance of about .+-.0.030 inches. The plurality of points is
joined with smooth continuous arcs. Each of the coordinates for the
T datum in Table 1 is adjusted based on a difference between a
datum distance W2 of the turbine blade and a reference datum
distance W2 associated with Table 1.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic view of an exemplary rotary
machine;
[0009] FIG. 2 is a partial sectional view of a portion of an
exemplary rotor assembly that may be used with the rotary machine
shown in FIG. 1;
[0010] FIG. 3 is a perspective view of a pressure side of an
exemplary turbine blade that may be used with the rotor assembly
shown in FIG. 2;
[0011] FIG. 4 is a perspective view of an exemplary turbine blade
shank, dovetail, and platform that may be used with the turbine
blade shown in FIG. 3;
[0012] FIG. 5 is sectional view of a shank of the exemplary turbine
blade shown in FIG. 3, illustrating a plurality of datums S, T, V,
and W defined with respect to the exemplary turbine blade shown in
FIG. 3;
[0013] FIG. 6 is a sectional view illustrating an exemplary profile
of an underside of a downstream angel wing and a portion of a
downstream cover plate of the turbine blade shown in FIG. 3;
[0014] FIG. 7 is a schematic perspective view of another exemplary
profile of a shank of the turbine blade shown in FIG. 3; and
[0015] FIG. 8 is a flow diagram illustrating an exemplary method of
modifying the shank of a turbine blade, such as the exemplary
turbine blade shown in FIG. 3.
DETAILED DESCRIPTION
[0016] The embodiments described herein include a turbine blade
shank in which portion of a downstream angel wing, and a portion of
a downstream cover plate radially inward of that angel wing,
cooperate to facilitate reducing a mean stress concentration and a
vibratory stress concentration induced to an intersection of the
downstream cover plate, a pressure side face, and a dovetail of the
blade. In some embodiments the shank of an existing turbine blade
may be modified by removing at least one of a first portion of
material from an underside of the downstream angel wing, a second
portion of material from a generally axially-extending portion of
the downstream cover plate adjacent the dovetail, and a third
portion of material from a generally radially-extending portion of
the downstream cover plate radially inward of the downstream angel
wing. In at least some embodiments, the stress reduction benefits
are achieved without modifying the dovetail, such that no
corresponding modifications to the rotor disk are required to
accommodate the modified blade.
[0017] Unless otherwise indicated, approximating language, such as
"generally," "substantially," and "about," as used herein indicates
that the term so modified may apply to only an approximate degree,
as would be recognized by one of ordinary skill in the art, rather
than to an absolute or perfect degree. Accordingly, a value
modified by a term or terms such as "about," "approximately," and
"substantially" is not to be limited to the precise value
specified. In at least some instances, the approximating language
may correspond to the precision of an instrument for measuring the
value. Here and throughout the specification and claims, range
limitations may be identified. Such ranges may be combined and/or
interchanged, and include all the sub-ranges contained therein
unless context or language indicates otherwise. Additionally,
unless otherwise indicated, the terms "first," "second," etc. are
used herein merely as labels, and are not intended to impose
ordinal, positional, or hierarchical requirements on the items to
which these terms refer. Moreover, reference to, for example, a
"second" item does not require or preclude the existence of, for
example, a "first" or lower-numbered item or a "third" or
higher-numbered item. As used herein, the term "upstream" refers to
a forward or inlet end of a gas turbine engine, and the term
"downstream" refers to a downstream or nozzle end of the gas
turbine engine.
[0018] FIG. 1 is a schematic view of an exemplary rotary machine
100. In the exemplary embodiment, rotary machine 100 is a gas
turbine engine. Alternatively, rotary machine 100 is any other
turbine engine and/or rotary machine, including, without
limitation, a steam turbine engine, a gas turbofan aircraft engine,
other aircraft engine, a wind turbine, a compressor, and/or a pump.
In the exemplary embodiment, gas turbine 100 includes an intake
section 102, a compressor section 104 that is coupled downstream
from intake section 102, a combustor section 106 that is coupled
downstream from compressor section 104, a turbine section 108 that
is coupled downstream from combustor section 106, and an exhaust
section 110 that is coupled downstream from turbine section 108.
Turbine section 108 is coupled to compressor section 104 via a
rotor shaft 112. In the exemplary embodiment, combustor section 106
includes a plurality of combustors 114. Combustor section 106 is
coupled to compressor section 104 such that each combustor 114 is
in flow communication with the compressor section 104. Turbine
section 108 is further coupled to a load 116 such as, but not
limited to, an electrical generator and/or a mechanical drive
application. In the exemplary embodiment, each compressor section
104 and turbine section 108 includes at least one rotor assembly
118 that is coupled to rotor shaft 112.
[0019] FIG. 2 is a partial sectional view of a portion of an
exemplary rotor assembly 118. In the exemplary embodiment, turbine
section 108 includes a plurality of stages 200 that each include a
stationary row 212 of stator vanes 202 and a row 214 of rotating
turbine blades 204. Turbine blades 204 in each row 214 are spaced
circumferentially about, and extend radially outward from, a rotor
disk 206. Each rotor disk 206 is coupled to rotor shaft 112 and
rotates about a centerline axis 208 that is defined by rotor shaft
112. A turbine casing 210 extends circumferentially about rotor
assembly 118 and stator vanes 202. Stator vanes 202 are each
coupled to turbine casing 210 and each extends radially inward from
casing 210 towards rotor shaft 112. A combustion gas path 216 is
defined between turbine casing 210 and each rotor disk 206. Each
row 212 and 214 of turbine blades 204 and stator vanes 202 extends
at least partially through a portion of combustion gas path
216.
[0020] With reference to FIGS. 1 and 2, during operation, intake
section 102 channels air towards compressor section 104. Compressor
section 104 compresses air and discharges compressed air into
combustor section 106 and towards turbine section 108. The majority
of air discharged from compressor section 104 is channeled towards
combustor section 106. More specifically, pressurized compressed
air is channeled to combustors 114 wherein the air is mixed with
fuel and ignited to generate high temperature combustion gases. The
combustion gases are channeled towards combustion gas path 216,
wherein the gases impinge upon turbine blades 204 and stator vanes
202 to facilitate imparting a rotational force on rotor assembly
118.
[0021] FIG. 3 is a perspective view of a pressure side of an
exemplary turbine blade 204. FIG. 4 is a perspective view of an
exemplary shank 224, a dovetail region 226, and platform 222 for
use with exemplary blade 204. With reference to FIGS. 2-4, in the
exemplary embodiment, each turbine blade 204 includes an airfoil
218 that extends radially between a root end 244 and a tip end 220
and that defines a pressure side 240 and an opposite suction side
242. Further in the exemplary embodiment, each turbine blade 204
includes a tip shroud 248 extending from tip end 220 of airfoil
218, a platform 222 coupled to root end 244, a shank 224 that
extends radially inwardly from platform 222, and dovetail region
226 that extends radially inwardly from shank 224 and that is
shaped to facilitate secure coupling of blade 204 to rotor disk
206. More specifically, in the exemplary embodiment, dovetail 226
is characterized by a wavy outer surface that is shaped to be
received within a complementarily shaped slot (not shown) defined
in rotor disk 206. In alternative embodiments, dovetail 226 has any
other suitable shape that enables blade 204 to function as
described herein. Platform 222 at least partially defines a
radially inner boundary of hot gas path 216. In alternative
embodiments, each blade 204 includes any suitable structure that
enables blade 204 to function as described herein.
[0022] In the exemplary embodiment, shank 224 includes an upstream
cover plate 228 and a downstream cover plate 230. Upstream cover
plate 228 and downstream cover plate 230 each extend radially
between dovetail 226 and platform 222, and laterally from a
pressure side face 250 to an opposite suction side face 252 of
shank 224. An upstream angel wing 232 extends axially upstream,
relative to hot gas path 216, from upstream cover plate 228, and
extends laterally along a face of upstream cover plate 228. A
downstream angel wing 234 extends axially downstream from
downstream cover plate 230, and extends laterally along a face of
downstream cover plate 230. In alternative embodiments, blade 204
includes any suitable number of each of upstream angel wings 232
and downstream angel wings 234, including zero, that enables blade
204 to function as described herein.
[0023] A region 237 of blade 204 encompasses, and is defined
generally proximate, an intersection of cover plate 230, pressure
side face 250, and dovetail 226. In some embodiments, when blade
204 is in operation in gas turbine 100, a mean stress concentration
and a vibratory stress concentration of blade 204 both may occur
proximate region 237.
[0024] FIG. 5 is a sectional view of shank 224 of turbine blade 204
illustrating a plurality of datums S, T, V, and W defined with
respect to blade 204. FIG. 6 is a sectional view illustrating a
profile 231 of an underside of downstream angel wing 234 and a
portion of downstream cover plate 230 radially inward of downstream
angel wing 234, illustrating a datum B defined with respect to
blade 204. The plurality of datums B, S, T, V, and W may be used to
establish a location of any point on blade 204, as will be
described herein. In the exemplary embodiment, primary datum S is a
radially extending plane defined with respect to at least one
physical feature of blade 204 such that datum S bisects shank 224.
Secondary datum B is a plane defined perpendicular to a radially
extending line through airfoil 218, and hence perpendicular to
datum S, at a radial location established by a top point of
downstream angel wing 234. Tertiary datum W also is a radially
extending plane defined perpendicular to each of datum S and datum
B, and intersects datum S at a distance W2 from datum target point
W1, taken parallel to datum B along datum S as shown in FIG. 5.
Finally, a pair of radially extending, orthogonal datums T and V
are respective planes rotated at angle V1 in a counterclockwise
direction with respect to the view of FIG. 5, from orthogonal
datums S and W, about the line of intersection of datums S and W.
Datums B, T, and V will be used herein to provide identifiable
reference points for a surface of turbine blade 204.
[0025] More specifically, profile 231 is defined by a plurality of
points identified as P01, P02, . . . , P25 and joined with smooth
continuous arcs. Table 1 below is an exemplary table of
coordinates, relative to datums B, T, and V described above, for
plurality of points P01, P02, . . . , P25 for an exemplary
embodiment of profile 231. More specifically, with reference to
FIGS. 4-6, the values in Table 1 are generated and shown to three
decimal places, in inches, based on an exemplary reference distance
W2 of 2.529 inches, and an exemplary reference angle V1 of
15.5.degree..
TABLE-US-00001 TABLE 1 B T V P01 0.000 3.456 0.794 P02 0.108 3.456
0.792 P03 0.210 3.427 0.790 P04 0.277 3.343 0.788 P05 0.318 3.243
0.787 P06 0.342 3.138 0.787 P07 0.363 3.031 0.787 P08 0.384 2.925
0.786 P09 0.405 2.819 0.786 P10 0.426 2.713 0.785 P11 0.454 2.608
0.785 P12 0.498 2.510 0.784 P13 0.566 2.426 0.782 P14 0.657 2.368
0.780 P15 0.761 2.341 0.778 P16 0.869 2.341 0.776 P17 0.974 2.367
0.774 P18 1.073 2.410 0.772 P19 1.157 2.477 0.770 P20 1.216 2.568
0.769 P21 1.258 2.668 0.768 P22 1.290 2.771 0.767 P23 1.317 2.876
0.767 P24 1.361 2.971 0.766 P25 1.439 3.046 0.764
[0026] In certain embodiments, a shape of an underside of
downstream angel wing 234 and a portion of downstream cover plate
230 radially inward from downstream angel wing 234 is defined by a
cylindrical rotation, about a radially-extending axis 235 using a
cylinder radius 233 that is substantially parallel to the B datum
plane, of profile 231, and between pressure side face 250 and
opposite suction side face 252 of shank 224. In some such
embodiments, it has been determined that shaping the underside of
downstream angel wing 234 and the portion of downstream cover plate
230 radially inward of downstream angel wing 234, according to the
cylindrical rotation of profile 231 shifts a mean stress
concentration and a vibratory stress concentration away from each
other proximate region 237 (shown in FIG. 4), as compared to at
least some known blades, thereby facilitating a reduced fatigue of
blade 204 and improving an operational life cycle of blade 204,
while maintaining an acceptable structural performance of blade
204.
[0027] Alternatively, in some embodiments, the shape of the
underside of downstream angel wing 234 and the portion of
downstream cover plate 230 radially inward from downstream angel
wing 234 is defined by a straight translation, along an axis
extending substantially perpendicularly to the V datum plane, of
profile 231 between pressure side face 250 and opposite suction
side face 252 of shank 224. In some such embodiments, it has been
determined that shaping the underside of downstream angel wing 234
and the portion of downstream cover plate 230 radially inward from
downstream angel wing 234 according to the straight translation of
profile 231 also shifts the mean stress concentration and the
vibratory stress concentration away from each other proximate
region 237 (shown in FIG. 4), as compared to at least some known
blades. As such, fatigue of blade 204 is facilitated to be reduced
and an operational life cycle of blade 204 is improved, while an
acceptable structural performance of blade 204 is maintained. In
some embodiments, the relative displacement of the mean stress
concentration and the vibratory stress concentration is not as
great within the straight translation of profile 231 as within the
cylindrical rotation described above, but nevertheless produces a
significant advantage over known blades. Moreover, in some such
embodiments, a straight translation of profile 231 facilitates
reducing a manufacturing complexity of blade 204 as compared to
cylindrical rotation of profile 231.
[0028] In addition, at least some embodiments include variations in
the datum values set forth in Table 1 while preserving the
advantages described above to a substantial degree. For example, in
some embodiments, either manufacturing tolerances and/or protective
coatings can cause each datum value listed in Table 1 to vary
within a tolerance of about .+-.0.030 inches, while preserving the
advantages described above to a substantial degree. Accordingly,
the values for profile 231 given in Table 1 are for a nominal
profile 231, and are subject to a tolerance. It will therefore be
appreciated that typical tolerances, i.e., .+-.values, including
any coating thicknesses, are additive to the distance from a given
datum given in Table 1.
[0029] Moreover, the nominal datum values in Table 1 are applicable
as described above to a range of values of angle V1. More
specifically, the nominal datum values in Table 1 are applicable as
described above to values of angle V1 that are within a range of
about .+-.10 percent from the exemplary value of angle V1
associated with Table 1.
[0030] In addition, the nominal datum values in Table 1 are
scalable to a range of values of distance W2. More specifically, in
embodiments in which datum distance W2 of blade 204 differs from
the reference datum distance W2 associated with Table 1, but
remains in a range of between about 2.00 inches and about 3.00
inches, each of the values for the T datum in Table 1 can be
adjusted by an amount equal to the difference between datum
distance W2 and reference datum distance W2, multiplied by the
cosine of angle V1 of blade 204, such that the advantages described
above are substantially preserved. As an illustrative example, in
one embodiment, W2 for an alternative blade 204 is 2.400 inches and
angle V1 remains 15.5.degree., and each of the values for the T
datum in Table 1 are adjusted by an amount equal to the difference
between datum distance W2 and reference datum distance W2,
multiplied by the cosine of angle V1, that is, by
(2.400-2.529)*cos(15.5.degree.)=-0.124 inches.
[0031] FIG. 7 is a schematic perspective view of another exemplary
turbine blade 204, illustrating an exemplary method 800 of
modifying shank 224 of turbine blade 206 from an initial profile
731 (illustrated as a solid line) to an undercut profile 732
(illustrated as a dashed line). FIG. 8 is a flow diagram of method
800. More specifically, in the exemplary embodiment, a portion of
downstream cover plate 230, including downstream angel wing 234, of
a blade 204 having initial profile 731 is modified, such as, but
not limited to, via a machining process, to replace initial profile
731 with undercut profile 732.
[0032] In some embodiments, method 800 includes removing 802 a
first portion 740 of material from an underside of downstream angel
wing 234. For example, in some embodiments, a maximum thickness 742
in a range of between about 0.070 inches to about 0.150 inches is
removed from the underside of downstream angel wing 234. In another
example, in the exemplary embodiment, a material having a maximum
thickness 742 of about 0.100 inches is removed from the underside
of downstream angel wing 234. In some such embodiments, it has been
determined that removing first portion 740 of material from the
underside of downstream angel wing 234 shifts the mean stress
concentration and the vibratory stress concentration away from each
other proximate region 237 (shown in FIG. 4), as compared to a
blade 204 having an initial profile 731, thereby facilitating a
reduced fatigue of blade 204 and improving an operational life
cycle of blade 204, while maintaining an acceptable structural
performance of blade 204.
[0033] Additionally or alternatively, in some embodiments, method
800 includes removing 804 a second portion 750 of material from a
generally axially-extending portion of downstream cover plate 230
adjacent dovetail 226. For example, in some embodiments, material
having a maximum thickness 752 in a range of about 0.020 inches to
about 0.040 inches is removed from the generally axially extending
portion of downstream cover plate 230 adjacent dovetail 226. In
another example, in the exemplary embodiment, material having a
maximum thickness 752 of between about 0.030 inches is removed from
the generally axially-extending portion of downstream cover plate
230 adjacent dovetail 226. In some such embodiments, it has been
determined that removing second portion 750 of material from the
generally axially-extending portion of downstream cover plate 230
adjacent dovetail 226 shifts the mean stress concentration and the
vibratory stress concentration away from each other proximate
region 237 (shown in FIG. 4), as compared to a blade 204 having an
initial profile 731, thereby facilitating a reduced fatigue of
blade 204 and improving an operational life cycle of blade 204,
while maintaining an acceptable structural performance of blade
204.
[0034] Additionally or alternatively, in some embodiments, method
800 includes removing 806 a third portion 760 of material from a
generally radially-extending portion of downstream cover plate 230
radially inward of downstream angel wing 234. For example, in some
embodiments, material having a maximum thickness 762 in a range of
about 0.050 inches to about 0.070 inches is removed from the
generally radially-extending portion of downstream cover plate 230
radially inward of downstream angel wing 234. In another example,
in the exemplary embodiment, material having a maximum thickness
752 of about 0.060 inches is removed from the generally
radially-extending portion of downstream cover plate 230 radially
inward of downstream angel wing 234. In some such embodiments, it
has been determined that removing third portion 760 of material
from the generally radially-extending portion of downstream cover
plate 230 radially inward of downstream angel wing 234 shifts the
mean stress concentration and the vibratory stress concentration
away from each other proximate region 237 (shown in FIG. 4), as
compared to a blade 204 an having initial profile 731, thereby
facilitating a reduced fatigue of blade 204 and improving an
operational life cycle of blade 204, while maintaining an
acceptable structural performance of blade 204.
[0035] In addition, in at least some embodiments, removal of at
least two of first portion 740, second portion 750, and third
portion 760 produces enhanced relative displacement of the mean
stress concentration and the vibratory stress concentration
proximate region 237 (shown in FIG. 4), as compared to removing
solely one of first portion 740, second portion 750, and third
portion 760. Moreover, in at least some embodiments, removal of all
of first portion 740, second portion 750, and third portion 760
produces enhanced relative displacement of the mean stress
concentration and the vibratory stress concentration proximate
region 237, as compared to removing just one or two of first
portion 740, second portion 750, and third portion 760.
Nevertheless, substantial benefits are still obtainable by removing
solely one or two of first portion 740, second portion 750, and
third portion 760. Moreover, in all such embodiments, relative
displacement of the mean stress concentration and the vibratory
stress concentration proximate region 237 is obtained without
modification of dovetail 226, thereby facilitating an avoidance of
any requirement to modify a slot (not shown) defined in rotor disk
206 to receive modified blade 204.
[0036] In some embodiments, a shape of an underside of downstream
angel wing 234 and a portion of downstream cover plate 230 radially
inward of downstream angel wing 234 is defined by a cylindrical
rotation of undercut profile 732 between pressure side face 250 and
opposite suction side face 252 of shank 224, as described above. In
alternative embodiments, the shape of the underside of downstream
angel wing 234 and the portion of downstream cover plate 230
radially inward of downstream angel wing 234 is defined by a
straight translation of undercut profile 732 between pressure side
face 250 and opposite suction side face 252 of shank 224, as
described above.
[0037] Moreover, in at least some embodiments, undercut profile 732
is identical to profile 231, as discussed above, including scaling
and manufacturing tolerances, with respect to FIG. 6 and Table 1.
In some such embodiments, profile 732 identical to profile 231,
which involves removing each of first portion 740, second portion
750, and third portion 760, results in a particularly advantageous
relative displacement of the mean stress concentration and the
vibratory stress concentration proximate region 237, and thus a
particularly advantageous reduction of fatigue on blade 204, while
maintaining an acceptable structural performance of blade 204. In
alternative embodiments, substantial advantages are obtained with
undercut profile 732 implemented as other than profile 231.
[0038] The above-described embodiments of turbine blades and
methods of modifying a shank of a turbine blade overcome at least
some disadvantages of known turbine blades. Specifically, a profile
of an underside of a downstream angel wing and a portion of a
downstream cover plate radially inward of the downstream angel wing
facilitates separating and/or reducing a mean stress concentration
and a vibratory stress concentration proximate an intersection of
the downstream cover plate, a pressure side face, and a dovetail of
the blade. Also specifically, in some embodiments, the shank of an
existing turbine blade is modified by removing at least one of a
first portion of material from an underside of the downstream angel
wing, a second portion of material from a generally
axially-extending portion of the downstream cover plate adjacent
the dovetail, and a third portion of material from a generally
radially-extending portion of the downstream cover plate radially
inward of the downstream angel wing to obtain the benefits of the
profile described above. In at least some embodiments, these
benefits are achieved without modifying the dovetail, such that no
corresponding modifications to the rotor disk are required to
accommodate the modified blade.
[0039] Exemplary embodiments of a turbine blade for use in a gas
turbine engine and methods for fabricating the same are described
above in detail. The methods and apparatus are not limited to the
specific embodiments described herein, but rather, components of
systems and/or steps of the method may be utilized independently
and separately from other components and/or steps described herein.
For example, the methods and apparatus may also be used in
combination with other rotary machines and methods, and are not
limited to practice with only the gas turbine engine assembly as
described herein. Rather, the exemplary embodiment can be
implemented and utilized in connection with many other rotary
machine applications.
[0040] Although specific features of various embodiments of the
invention may be shown in some drawings and not in others, this is
for convenience only. Moreover, references to "one embodiment" in
the above description are not intended to be interpreted as
excluding the existence of additional embodiments that also
incorporate the recited features. In accordance with the principles
of the invention, any feature of a drawing may be referenced and/or
claimed in combination with any feature of any other drawing.
[0041] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
* * * * *